A central processing unit, and a chip set assembly (such as a north bridge chip set, a south bridge chip set) of the new version are provided with precise and complicated structure in such a manner to result in high performance and fast computing power thereof. As the computing capability of the PC increases, the temperature of the central processing unit and the chip set assembly subsequently gets higher when under operation. It is the trench and object of the manufacturers of the mother board to lower the temperature of these components around the central processing unit so as to prevent from malfunction due to the rise in the temperature of electronic components around the central processing unit.
A heat dissipating device is provided on the mother board, and includes a first suction fan disposed on the central processing unit via a heat sink and a second suction fan mounted on the computer housing. The heat sink on the first suction fan has a fin configuration so as to be adapted to guide the airflow toward the chip assembly in order to lower the actual temperature of the chip assembly. The second suction fan on the computer housing draws the air outwardly so as to cause an air circulation, which, in turn, results in an increase of the air density within the computer housing so as to enhance the heat dissipating effect of the CPU and the chip assembly.
FIG. 1 is a fragmentary view of a conventional mother board 1 which includes a CPU 2, a suction fan 12 mounted on the CPU 2 via a first heat sink 11, and a plurality of electronic components. The electronic components may includes a RAM (random access memory) module disposed at a left side of the CPU 2, and a row of capacitors 14 and a row of power-consumption components 15 disposed at a right side of the CPU 2. A north bridge chip set 3 (not visible) is mounted on the mother board 1 at a rear side of the CPU 2. A second heat sink 16 is mounted above the north bridge chip set 3, and is formed with a plurality of fins 16a for heat dissipation. An expansion card 17 is disposed adjacent to the second heat sink 16 away from the CPU 2. The first heat sink 11 is formed with a plurality of fins (not visible since covered by the suction fan 12) so as to guide the air flow from the suction fan 12 toward the second heat sink 16, thereby lowering the temperature of outer surface of the north bridge chip set 3.
It is noted that in addition to the north bridge chip set 13, the power transistors (mostly made up of MOSFET) disposed at the right side of the CPU generates a relatively high temperature under operation. Under the predetermined output rate, the temperature of the power transistors 15 may exceed 100° C. Though these power transistors 15 can operate under a temperature that is higher than that of the CPU or the chip assembly, the constant operation of the power transistors above 100° C. can result in melting of the tin, which is used for mounting the power transistors on the mother board. Since the mother board 1 is mounted uprightly in the computer housing, displacement and disengagement of these power transistors on or from the mother board 1 can adversely affect the functions of the mother board 1.